28 Aug Winter Peas vs Spring Peas: What’s the Real Difference?
As autumn harvest continues, planning and seeding of winter crops is starting. A popular winter crop in both Canada and the US is winter peas. If this is your first time planting them you may be asking: how are they different from spring peas? And how should I plan for a winter pea crop? In this week’s Growing Possibilities, we will explore what makes winter peas unique from their spring-sown equivalents, and how you can prepare for a successful crop this winter.
Winter and spring varieties are still of the same species, just different bred varieties that have led to adaptations for cold-hardiness. These factors include transitioning from vegetative to flowering stages sooner, resulting in their maturity two to four weeks earlier than spring varieties (1).
Winter peas are often chosen as a winter cover crop for their additions of nitrogen to soil. This is the same with spring peas, which are also chosen in a crop rotation to boost soil nitrogen, but winter peas have the advantage when providing nitrogen (N) back into soil. Spring peas fix N for approximately 8 weeks during the growing season. Winter peas, which split their N fixation between autumn months and the following spring, fix N for a total of approximately 12-16 weeks (1). This leads to additions of 90-150 lbs/acre of N into soil (2).
Seeding for winter peas is comparable to spring peas in most aspects, with a major difference being field conditions during seeding. Seeding winter peas into grain stubble, or interseeding with a winter grain variety is recommended, as these environments will help to protect the roots of your young winter peas from soil heaving from freezing and thawing, and by trapping snow. Snow trapped by field stubble provides valuable insulation for winter peas, as they will die in sustained cold below -8°C (18°F) (3). When seeding winter peas, earlier is better, with plants entering freezing soil conditions with 6-8 inches of stand having the best survivability (3).
Winter peas, just like spring peas, form symbiotic relationships with soil bacteria to fix N from the air. A rhizobial inoculant is recommended for winter pea seeds to guarantee nodulation and maximize N fixation (3). Just make sure that the inoculant you choose is confirmed to be applicable to winter pea varieties, such as XiteBio® PulseRhizo®, as not all rhizobial inoculants rated for spring peas, may not be very effective on winter pea varieties.
Spring and winter pea varieties are both susceptible to similar weeds, but the spectrum of weed species that target winter peas are different, and not all herbicides registered for use on spring varieties show the same effectiveness on winter ones. Use of herbicide use on winter peas is not only about choosing an effective option, but also in the application timing. Herbicide application timing for winter peas comes shortly after crop dormancy is broken. These early spring conditions often have below freezing temperatures, especially overnight, which reduces the effectiveness of many registered herbicides (1).
1) McGee, R.J., Eigenbrode, S., Nelson , H., Schillinger, W. (2017). Re‐inventing Austrian winter pea towards developing food quality winter peas. Crops & Soils, 50(4). https://doi.org/10.2134/cs2017.50.0401
2) Clark, Andy. Managing Cover Crops Profitably (3rd ed.). 2008. Beltsville, MD: Sustainable Agriculture Network. P. 135- 141. ISBN: 1437903797, 9781437903799.